Download INTRODUCTION "Trigeminal Neuralgia (TN) is the worst pain in the

Dr. Timmy Chan
Anaesthetist and Pain Specialist
Department of Anaesthesiology, Queen Mary Hospital
MBBS, FANZCA, FHKCA, FHKAM, FHKCA (Pain Medicine), Dip. Pain Mgt. (HKCA), FIPP
INTRODUCTION
"Trigeminal Neuralgia (TN) is the worst pain in the world,”.This is stated in “Striking Back” by the
Trigeminal Neuralgia Association [1]. Trigeminal neuralgia is a painful condition of the face. TN is
the most common form of facial pain in people older than 50 years. The highest incidence occurs in
the ages between 50 and 70 years. TN is more prevalent in women than men with a ratio of 1.5:1
[2].
A survey conducted in 6 European countries indicated that trigeminal neuralgia significantly
impacted the quality of life and the socioeconomic functioning of affected patients. [3]. According
to International Association for the Study of Pain (IASP), year 2014 is the Global Year Against
Orofacial Pain. This signifies the increased awareness of TN internationally.
PATHOPHYSIOLOGY
It is unclear. But compression of trigeminal ganglion near the origin of the brain steam near the
origin of the brain stem by vessels or tumor, may be the possible cause. Such compression causes
demyelination that leads to abnormal depolarization resulting in ectopic impulses and pain.
SYMPTOMS
TN is recognized by
- Unilateral,
- short-lived,
- strong, lancinating, " electric shock" like shooting pains in 1 or more branches of the fifth cranial
nerve.
The pain is triggered by ordinary stimuli, such as eating, washing, shaving, cold, warmth, and even
talking.
The distribution of the pain in the various branches of the trigeminal nerve is stated below [2].
V1 only
V2 only
V3 only
4%
17%
15%
V2+V3
V1+V2
V1+V2+V3
32%
14%
17%
DIFFERENTIAL DIAGNOSES
There are essential and secondary TN.
For the differential diagnoses of essential TN, the most important differential diagnostic
considerations are specific facial pain, nonspecific facial pain, temporomandibular arthrosis, dental
disorders, and vascular migraine etc. [4].
Six questions for history taking [4] for essential TN
1. Does the pain occur in attacks?
2. Are most of the attacks of short duration (seconds to minutes)?
3. Do you sometimes have extremely short attacks?
4. Are the attacks unilateral?
5. Do the attacks occur in the region of the trigeminal nerve?
6. Are there unilateral autonomic symptoms?
For secondary TN, it is usually due to other problems e.g.tumor of the cerebellopontine angle or
multiple sclerosis.
PHYSICAL EXAMINATION
Cranial nerve examination and other neurological exam needed to be done.
For idiopathic TN, neurological examination is usually unremarkable.
For secondary TN, there may be positive neurological signs, indicating underlying pathology.
INVESTIGATIONS
It is important that MRI of the brain should be carried out in each patient so as to exclude secondary
TN such as a tumor or multiple sclerosis, or vascular compression of the trigeminal nerve in the
posterior cranial fossa, especially before interventional pain procedures.
TREATMENT
(A) For conservative treatment (according to IASP fact sheet)
Medical treatment of TN is based on the use of antiepileptic drugs.
First-line therapy should be carbamazepine (200–1200 mg/day) and oxcarbazepine (600–1800
mg/day), according to current evidence-based treatment guidelines. Second-line treatment is based
on little evidence and includes add-on therapy with lamotrigine (400 mg/day) or a switch to
lamotrigine or baclofen (40–80 mg/day). Other antiepileptic drugs have been studied in small openlabel.
1.
2.
3.
4.
5.
6.
(B) Interventional treatment
Surgical microvascular decompression (MVD)
Stereotactic radiation therapy, Gamma knife
Percutaneous balloon microcompression
Percutaneous glycerol rhizolysis
Percutaneous radiofrequency (RF) treatment of the Gasserian ganglion
Gasserian ganglion stimulation/neuromodulation (experimental)
Surgical MVD
During MVD, the vessels that are in contact with the root entry zone are coagulated and arteries are
separated from the nerve using an inert sponge. It is, however, a major surgical procedure that
entails a craniotomy to reach the trigeminal nerve in the posterior fossa.
Efficacy:
- 90% of patients reporting initial pain relief and more than 80% remaining pain free after 1 year,
75% after 3 years, and 73% after 5 years, with sustained improvements in activities of daily
living. (IASP fact sheet)
Risks:
- The average mortality rate ranges from 0.2% to 0.5%, and up to 4% of patients suffer from major
problems such as cerebrospinal fluid leakage, infarcts, hematomas, or aseptic meningitis.
- The most common long-term complications include mild sensory loss (7%) and hearing loss
(10%) (IASP fact sheet).
For Stereotactic radiation therapy, Gamma knife, The Gamma knife
It involves high dose irradiation of a small section of the trigeminal nerve. It is a noninvasive
treatment that can be applied under local anesthetic and light sedation.
Efficacy:
- initial efficacy appears to be limited; between 60% and 70% indicate a reduction in pain.
- The long-term effects are not yet known. [5]
Disadvantages:
- Cost
- delayed onset of both pain relief (for an average of 1 month) and sensory loss.
Percutaneous balloon microcompression
The trigeminal nerve is compressed by a small balloon, which is percutaneously introduced into
Meckel’s cavity using a needle, causing ischaemia to the ganglion cells.
Percutaneous glycerol rhizolysis
During percutaneous glycerol rhizolysis, a needle is introduced into the trigeminal cistern,
visualized using fluoroscopy. In a seated patient, with the head flexed, a contrast dye can be
injected to determine the size of the cistern. Then, after the contrast dye is aspirated, an equal
volume of glycerol is injected.
Percutaneous RF Treatment of the Gasserian Ganglion
Efficacy:
- One year following radiofrequency thermocoagulation, 68–85% of patients are still pain free, but
after 3 years the percentage goes down to 54–64%, and after 5 years only 50% of patients are still
pain free (IASP fact sheet).
- The outcome of treatment of Gasserian ganglion is reportedly less favorable than with open
operation (MVD) but it is less invasive and has lower morbidity and mortality rates.
Risks:
- most common side effects are sensory loss (50%),
- paralysis of the Masseter muscle (4.1%)
- dysesthesias (6%),
- anesthesia dolorosa (4%),
- corneal numbness with a risk of keratitis (4%)
Gasserian Ganglion Stimulation/Neuromodulation (Experimental)
Gasserian ganglion electric stimulation was first described by Shelden et al. in 1967 for 3 patients
with trigeminal neuralgia [6]. More recently in 2007, Machado et al. reported percutaneous
Gasserian ganglion stimulation in 8 patients with trigeminal neuropathic pain. Only 3 patients
continued to have >50% pain improvement after 1 year of treatment [7]. In fact, people have tried to
have Gasserian ganglion electric stimulation, however the results were still suboptimal. This is
mainly due to difficulty in anchoring the leads. These techniques should only be reserved for
selected patients with intractable trigeminal neuropathic pain who failed to improve with other
conservative treatment.
SUMMARY
The first treatment of choice is carbamazepine or oxcarbazepine. In younger patients with TN, the
first choice is probably MVD. For elderly, RF treatment of Gasserian ganglion is recommended.
Clinical practice algorithm for the treatment of trigeminal neuralgia [8].
Evidence for interventional management of trigeminal neuralgia [9].
Technique
Radiofrequency treatment of
Gasserian ganglion
Evidence
2B +
Recommendation
Recommended
value of “2” when the benefit was closed
balanced with the risk and burden of possible
side effects.
“B” represents evidenced derived from RCTs
with methodological limitation or large
observational studies.
“+” +ve outcome
“-“ –ve outcome
Pulsed Radiofrequency treatment
of Gasserian ganglion
2B -
Negative recommendation
References:
1. Weigel G, Kenneth F, Casey M. Striking Back! Gainsville: Trigeminal Neuralgia Association;
2000
2. Rozen TD. Trigeminal neuralgia and glossopharyngeal neuralgia. Neurol Clin. 2004;22:185–
206
3. Tolle T, Dukes E, Sadosky A. Patient burden of trigeminal neuralgia: results from a cross-
4.
5.
6.
7.
8.
9.
sectional survey of health state impairment and treatment patterns in six European countries.
Pain Pract. 2006;6:153–160.
Nurmikko T. Trigeminal neuralgia and other facial neuralgias. In: Cervero F, Jensen TS, eds.
Handbook of Clini- cal Neurology, Vol. 81 (3rd Series. Vol. 3), Pain. New York: Elsevier;
2006:573–596
Young RF, Vermulen S, Posewitz A. Gamma knife radiosurgery for the treatment of trigeminal
neuralgia. Stereotact Funct Neurosurg. 1998;70(suppl 1):192–199.
Shelden CH, Pudenz RH, Doyle J. Electrical control of facial pain. Am J Surg. 1967;114:209–
212.
Machado A, Ogrin M, Rosenow JM, Henderson JM. A 12-month prospective study of gasserian
ganglion
Jan Van Zundert et. al., Evidence-based interventional pain medicine. According to clinical
diagnoses
van Kleef M, Mekhail N, Van Zundert J. Editorial; Evidence based guidelines for interventional
pain medicine according to clinical diagnoses. Pain Pract, 2009;9:247-251.]